Head capsule yellowish with dark postoccipital margin.
Antenna with 5 segments; segments consecutively shorter until fifth, which is longer than fourth. Ring organ low on basal segment. Blade shorter than flagellum. Lauterborn organs distinct, longer than segment 3.
All S setae described as simple but evidently SI can be apically finely divided apically into 2-3 fine branches. Labral lamellae absent. Pecten epipharyngis consisting of 3 long, smooth scales, with median scale slightly longer and broader. With 6 pairs of chaetulae laterales, long, simple; chaetulae basales weakly bifid at apex. Premandible with apical tooth; brush absent.
Apical tooth longer than combined width of 4 inner teeth. Seta subdentalis slightly bent at apex. Seta interna with 6-7 smooth branches.
Mentum with 2 median teeth and 6 pairs of lateral teeth; 2 first lateral teeth appressed toward median teeth. Ventromental plate broad, extending beyond margin of outer mental tooth; few but distinct setae (about 7) present in beard.
Pecten galearis with distinct base and weak, blunt teeth. Anterior lacinial chaeta broader than other lacinial chaetae.
Body (based on larval exuviae). Parapods normally developed; medium-sized claws of anterior parapods with some strong, inner teeth. Procercus squat to higher than wide; posteriorly darkened with small but distinct medioposterior spur; with 5 anal setae. Anal tubules present. Body setae apparently short and simple.
At the time of the Holarctic key, the only known larva was reared from a stream or river in Northwest Territory, Canada (Sæther, 1981a). A second species is described from an adult from Finland (Tuiskunen, 1985a). The illustrated larva comes from Lake Superior in North America.